Hey there guys, I have a 1997 Grand Am GT Coupe with around 153,000 miles on it. We just replaced the Throttle position sensor, Cam shaft position sensor, spark plugs and wires and I am still getting a cylinder misfire error when looking at the check engine log. When accelerating, my car will not pick up and go, but slowly accelerate.

Also, at around 55 mph, I will have my gas pedal steady or even using my cruise control.. but the RPM's will drop from around 2,000 down to 1,500. I will let off the gas and it will jump back up to 2,000 RPM's. Has anyone ever experienced something like this?? It was idling around 3,500 to 4,000 RPM until we changed the spark plugs and now it idles fine. Please let me know if you have any other questions about the car for diagnostic purposes!!!

chris_gt_74

02-07-2012 08:58 PM

Quote:

Originally Posted by xxallonblack
(Post 1171689)

Hey there guys, I have a 1997 Grand Am GT Coupe with around 153,000 miles on it. We just replaced the Throttle position sensor, Cam shaft position sensor, spark plugs and wires and I am still getting a cylinder misfire error when looking at the check engine log. When accelerating, my car will not pick up and go, but slowly accelerate.

Also, at around 55 mph, I will have my gas pedal steady or even using my cruise control.. but the RPM's will drop from around 2,000 down to 1,500. I will let off the gas and it will jump back up to 2,000 RPM's. Has anyone ever experienced something like this?? It was idling around 3,500 to 4,000 RPM until we changed the spark plugs and now it idles fine. Please let me know if you have any other questions about the car for diagnostic purposes!!!

Is it consistently the same cylinder that's misfiring or more than one? What plugs did you put in?

xxallonblack

02-08-2012 11:01 AM

I believe it is the same cylinder, and we got generic plugs and wires.. the cheapest from advanced auto. Originally it was the high idling that made us do the tune up, and now the idling issue is gone, it just bogs down and has the misfire code.

xxallonblack

02-08-2012 01:15 PM

I think the code was PO300.

chris_gt_74

02-08-2012 05:08 PM

Were you getting the misfire code prior to the plug and wire change? I think that code is a nonspecific misfire which could be multiple cylinders. If you weren't getting a misfire prior to the plugs I'd say that could be the problem even though they are brand new. NGK and AC/Delco Iridium plugs are the only 2 that I know for sure work well.

Of course the cam sensor could also be the trouble because it signals the plugs and such on when to fire. So it could be all jacked up.

CraiGT

02-09-2012 10:41 AM

First off, what engine do you have?

I think the rpm drop at cruising speeds is just the tc locking up for better mileage. Suppose to do that.

xxallonblack

02-09-2012 10:55 AM

Okay, I will have to replace the wires and plugs first. I just changed the cam sensor.. and when after that we did the plugs and wires. The wires and plugs were the cheapest because I did not have money at the time. Also, no I was not getting the code before we changed the plugs and wires, so we will start there!

@CraiGT the 3.4 L V6, I guess the standard on '97 GT Coupes? And with the tc locking up I guess that does sound possible, but I just never heard of that before and it has never done this before, or at least I never noticed it lol.

CraiGT

02-09-2012 10:22 PM

Thats standard for most cars. But not the 3400 part. That only came in the 99 and up Grand Ams. You should have the 3100. You need to verify this.

xxallonblack

10-06-2012 11:02 AM

Quote:

Originally Posted by CraiGT
(Post 1171779)

Thats standard for most cars. But not the 3400 part. That only came in the 99 and up Grand Ams. You should have the 3100. You need to verify this.

Yes, you were correct. It is the 3.1 L engine. There was a bad wire harness around the TPS/ throttle body that we replaced and it stopped the idling at 3k+ RPMs, not it is just slow to accelerate. Was having over heating issues, also. Replaced the water pump, coolant temp sensor, thermostat, heater core, flushed the radiator and put a 50/50 mixture in.

Since it is slow with acceleration, we thought it may be a fuel pressure problem. Changed the fuel filter, fuel pressure regulator, and it stays at around 20 psi - 24 psi. I was reading it should be above 35+? Is this correct? Also what problems could cause this? Changing the spark plugs and wires again in the near future.

TDavis

10-06-2012 11:24 AM

> Old thread.
> You finally answered back to him 8 months later.

K.

xxallonblack

10-06-2012 12:01 PM

Quote:

Originally Posted by TDavis
(Post 1188622)

> Old thread.
> You finally answered back to him 8 months later.

K.

Thank you for your constructive post, honestly haven't seen one this helpful. Props.

I forgot that I even posted on here and googled my issue and found this post, and once again posted in it. If were to start a new thread I'm sure you would have also replied saying "use the search" then I would search, find my thread that I already started, and probably would have gotten the same reply. So thank you again for the completely useless response.

TDavis

10-06-2012 12:06 PM

Quote:

Originally Posted by xxallonblack
(Post 1188626)

Thank you for your constructive post, honestly haven't seen one this helpful. Props.

I forgot that I even posted on here and googled my issue and found this post, and once again posted in it. If were to start a new thread I'm sure you would have also replied saying "use the search" then I would search, find my thread that I already started, and probably would have gotten the same reply. So thank you again for the completely useless response.